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Where is the String Theory

  1. Apr 29, 2010 #1
    Hello everyone,

    I have been interested by the String Theory and the M-Theory for quite a few years now, I read the Elegant Universe by Brian Greene (and watched the PBS documentary based on his book).

    This theory sounds really "elegant" indeed, but I was wondering what progress, if any, has been made in that field recently. Wikipedia states that it might be imcompatible with the notion of dark energy, as it would require a positive cosmologic constant and several things that makes it impossible to verify.

    In 2010, is the theory (or theories) still considered as serious among the physicists,
    or is there another theory that "seems" to be "closer to reality" ?

    I like to read and hear Brian Greene and Michio Kaky on this subject, however, I do not
    have enough knowledges in that field to know whether they are people more into the
    real science than philosophy of what an elegant theory would be.

    That's it for my first post on PF. I hope that I made myself clear, as it is not really easy
    to express my questions ;)
  2. jcsd
  3. Apr 29, 2010 #2
    Your understanding of the Wikipedia article is not quite correct. String theory is compatible with dark energy. There is no known physical phenomenon in direct contradiction of string theory.
    String theory, as a mainstream subject, is certainly considered serious, although it receives a bit less interest now. String theory is a theory of quantum gravity. There is no way to tell which theory of quantum gravity is "closer to reality", because only experiments can tell, and such experiments are completely beyond our capabilities.
    Kaku and Greene are not philosophers. They are physicists who occasionally use philosophical and aesthetic arguments such as "elegance" to promote the theory they believe. Still, elegance is vacuous by itself, and the only thing can decisively convince people of the correctness of string theory is experimental verification, which is not possible with today's technologies.
  4. Apr 29, 2010 #3
    String theory is as serious as ever, it is indeed receiving less interest, but only because it used to receive huge amounts before. It's still the number 1 area of high-energy physics. In fact, anybody working in high-energy would only be gimping himself by ignoring string theory. The thing is string theory lead to much more insight than originally expected. AdS/CFT, amplitude calculations in gauge theories and gravity (the famous (gravity)=(yang-mills)^2), and many other things are all products of string theory.

    The unification program, with its landscape and other issues, is just one small side of string theory. Even if this problem is completely unsolvable, or some prediction is made and it turns out wrong, string theory will still be useful for a number of other topics.

    Most people are of course more interested in unification, and that's what draws the crowd, but it's not the only thing to do in physics. And as it happens with anything, everyone goes for the low lying fruit first, and then gives up as it gets harder and harder. So the number of people working on string theory, or the hype surrounding it, is not really indicative of any merits the theory might have, I think.
  5. Apr 30, 2010 #4
    Right, it makes things a little more clear for me now.
    Thanks for your answers
  6. May 1, 2010 #5


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    "String theory is as serious as ever, it is indeed receiving less interest, but only because it used to receive huge amounts before. "

    Its about the same as before, the focus is simply less on pure theory as opposed to phenomenology and spinoffs like condensed matter/atomic physics and the like. Understandably too, since there are simpler, more readily solved problems there.

    Still if you go to the major centers of physics, generally speaking over half of the high energy staff are basically working on stringy material or stringy inspired material in general, and its still the dominant research direction in fundamental physics (many times over in fact).

    You simply can't go to a conference, where someone doesn't rehash AdS/CFT for instance.
  7. May 4, 2010 #6
    We have no clue if we are closer to reality with these theories because, frankly, we have no clue what reality is. To understand COMPLETELY what reality is we would have to A)be God or B) have quantified the univerese into some form of mathematical equation.
  8. May 4, 2010 #7


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    It depends what you mean by "reality". In physics "reality" can often be understood as a synonym for "collection of facts" w/o any deerp philosophical meaning. So if a theory predicts these facts correctly, then the theory describes reality.

    Of course this is not philosphy, but physicist's philosophy only ...
  9. May 4, 2010 #8
    Actually, I agree that reality wasn't the right term to use: By reality, I actually meant, like tom.stoer said: "a theory that predicts these facts correctly".
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